Preparation of furan-alpha, alpha&#39;-dicarboxylic acid esters



Patented Mar. 30, 1954 i i i UNITED STATES PATENT OFFICE PREPARATION OF FURAN-a,a'-DICAR- BOXYLIC ACID ESTERS Richard Kuhn and Karl Dury, Heidelberg, Germany No Drawing. Application July 16, 1951, Serial No. 237,078

1 Claim. (Cl. 260-3475) 1 2 This invention relates to the preparation of pure furan-e,a'-dicarboxylic acid diethyl ester is furan-u,a'-dicarboxylic acid esters. obtained.

If an a,a-diketoadipic acid ester or anoc,u'- In a corresponding manner from the dimethyl,

dihydroxymuconic acid ester or an acyl derivadipropyl and di-n-butyl esters of a,a-dihydroxytive of the latter, is treated with a dehydrating 5 muconic acid are obtained the dimethyl ester agent, e. g. concentrated sulfuric acid, ring (M. P. 107 C.),di-n-propyl ester (boiling point/12 closure occurs, even inthe cold, without saponlfimm, 164 C.) and the di-n-butyl ester (M. P. cation, to give a furan-a,a'-dica1'boxylic acid 40 C.) of furan-a,a'-dicarboxylic acid.

ester in practically quantitative yield. These The dehydration can also be effected by other esters are compounds of potential value as interagents, e. g. by heating with silver sulfate. mediates in chemical syntheses and. have valu- We claim:

able pharmacological properties. Thus fm'an- The method of preparing a furan-a,a'-dicara,cz'-diCaIb0Xy1iO acid diethyl ester has strong boxylic acid lower alkyl ester which comprises anesthetic action which is similar to that of 00- dissolving a lower alkyl diester of a dicarboxylic caine with respect to speed of initiation and dura- 15 acid selected from the group consisting of a,oz'-dition of total anesthesia (measured on the cornea ketoadipic acid, u,e'-dihydroxymuconic acid and of the rabbits eye). acyl derivatives of a,0c'dihyd1OXyml1C0niC acid in Examples concentrated sulfuric acid at room temperature, allowing the solution to stand until ring closure In th f ll win exampl s parts by Wei ht and has been effected, and precipitating the desired volume are to be taken in metric units. ester by diluting the reaction mixture with water 0118 P y Weight of a,a'-dihydr y while cooling to absorb the heat of dilution. acid diethyl ester is dissolved in 5 volumes of concentrated sulfuric acid and allowed to stand for RICHARD KUHN 2 hours at approximately 20 C. The mixture is 5 KARL DURY.

then poured on ice and crystallized from petroleum ether. The yield is 95% of the theory of References m the file of this Patent furan-a,a'dicarb0 y11c c d di yl ester 31S Fieser and Fieser, Organic Chemistry, pp. white needles having a melting point of 47 C. 54-56 1944) From a,e'-diacetoxymuoonic acid diethyl ester e t in, vol. 18, p punder the same conditions 98% of the theory of Chem- A vol. 38, 1- 1230- 

